In the related art, there is known a substrate processing apparatus including a plurality of single wafer type processing units that supply a processing liquid onto the front surface or the front and rear surfaces of a substrate so as to process the substrate by the processing liquid while holding and rotating the substrate such as, for example, a semiconductor wafer, and a transfer device that performs the carry-in/out of the substrate with respect to the processing units.
Some substrate processing apparatuses have adopted a layout in which processing units are stacked in multiple stages in order to obtain higher throughput while suppressing an increase in the footprint of the apparatus (see, e.g., Japanese Patent Laid-open Publication No. 2012-142404).